The present invention relates generally to a closure system for heat exchangers whereby fluids in first and second fluid passageways are positively sealed against leakage to the atmosphere and against interleakage between the passageways.
The closure system of the present invention is particularly suitable for use in connection with heat exchangers, examples of which are described in U.S. Pat. Nos. 3,018,090; 3,079,992; 3,109,671; 3,155,404; 3,377,087; 3,424,480; 3,593,782 and 3,948,315. Such heat exchangers can comprise an inner tube assembly with a plurality of U-shaped tubes with one end of the U comprising a fluid inlet for the tubes and the other end comprising a fluid outlet. The tubes are supported at each end in spaced relationship with respect to one another by a supporting member which is usually referred to as a tube sheet, and which comprises a generally disk-shaped element having a plurality of apertures through which the ends of the tubes extend.
The U-shaped tubes are supported within an outer shell assembly which is also of generally U-shaped configuration. The base of the shell assembly, however, adjacent the bend in the U-shaped tubes, is provided with a removable cover so that the assembly consisting of the tubes and the tube sheets in which they are mounted can be inserted into and withdrawn from the shell as a unit by sliding the assembly longitudinally through the arms of the shell. Once the tubes are in position within the shell, the cover is secured to the base of the shell in a fluid-tight manner.
A fluid inlet port is formed in the sidewall of the shell adjacent one end thereof, while a fluid outlet port is formed in the sidewall near the opposite end of the shell. A fluid is caused to circulate through the shell and around the plurality of tubes from the inlet port to the outlet port.
A closure member is attached to a terminal portion or member provided on each end of the shell, and each is formed with a conduit to permit another fluid to flow through the tubes from one end thereof to the other end in heat transfer relationship with the fluid circulating through the shell. These closure members, the terminal members of the shell, and the tube sheets mounted within each end of the shell, together with strategically positioned sealing means and appropriately constructed retaining means, comprise a closure system designed to prevent fluid leakage around the periphery of the tube sheets or to the atmosphere, as well as to prevent any longitudinal movement of the tubes relative to the shell.
A suitable closure system must be effective in preventing the fluid flowing into, through, and out of the plurality of tubes from leaking into and mixing with the fluid flowing through the interior of the shell, and vice versa, as well as in preventing either fluid from leaking out of the heat exchanger into the atmosphere. It must also be able to reliably withstand the very substantial pressures at which the fluid is frequently pumped through the plurality of tubes in heat exchangers of this type. In addition, it is important that the closure system be designed such that the heat exchanger can be easily disassembled to permit removal of the tube and tube sheet assembly from the shell or otherwise provide ready access to the interior of the heat exchanger for inspection, cleaning, or repair and, thereafter, quickly reassembled for use. It is also desirable that the closure system be relatively simple mechanically with a minimum number of easily made components so as to provide a structure that is economical to manufacture and long lasting. In this regard, many known closure systems are designed with sealing surfaces of tapered or even more complex configuration. Such surfaces require accurate alignment with respect to one another; and if any one surface becomes damaged and requires machining, it is usually necessary that other sealing surfaces also be machined.